Sasuke is often also a key character. His relationship with Naruto is a major part of the Naruto series, and in this fanfiction, Naruto might try to change Sasuke's path in the past. So, Sasuke's character development in this new timeline is an important aspect.
Naruto is usually a main focus. Since it's about going back in time, his character is central as he has the knowledge of the future to change things.
Obviously, Harry Potter himself is still a main focus. His life 19 years after the end of the original story, how he has matured, and his role in the wizarding world. Ginny Weasley is also important as his wife. Their children may also be central characters in some fanfictions.
The main character is Naruto without a doubt. But characters like Sasuke can also be important in these fanfics. Sasuke, as Naruto's rival, may be shown to have a different perspective on Naruto's past. Maybe he discovers something about Naruto's family or his own family's connection to Naruto's past that was previously unknown. And the Sannin, including Tsunade, could also be significant as they were part of the older generation with knowledge of events that could be related to Naruto's past.
Obviously, Lucifer is one of the main focuses. Since it's a Lucifer - centered fanfiction, his actions, thoughts, and development would be central.
Well, obviously Batman and Batgirl are the main ones. Batman is often shown dealing with his complex relationship with the Joker and also his feelings towards Batgirl, especially in the context of the disturbing events of 'The Killing Joke'.
Naruto is the central character in 'naruto dark naruto fanfiction'. But characters like Orochimaru can play a big role. He might see an opportunity in a darker Naruto and try to manipulate him for his own gain. Hinata could also be a main character in some fanfictions. Her love for Naruto might be put to the test as she tries to understand and save Naruto from his dark path. And the Sannin, especially Jiraiya, might be involved as they were important in Naruto's development in the original and could have a role in dealing with his new, darker nature.
In addition to the main characters from the original series, some fanfictions in 'naruto paragon fanfiction' might introduce new characters. These could be characters with unique abilities or backstories that interact with Naruto and the gang. They might be from a long - lost clan or have a special connection to an ancient ninja art, which then becomes intertwined with Naruto's journey in the fanfiction.
Naruto is often a central character. Since he has such a complex personality in the original series, fanfiction writers like to explore different aspects of him in the context of duality. They might show his struggle between his role as a hero and his inner insecurities.
Naruto is usually a main focus. Since the concept is related to perfection, his journey to become the best Hokage and the strongest ninja is often explored in greater detail. He might be shown overcoming his flaws more quickly or mastering new techniques faster. Sasuke is also likely to be a central character. His path of revenge and his own pursuit of power can be re - imagined with the idea of perfection, like achieving the ultimate Sharingan or new levels of his combat skills.
Obviously, Naruto is one of the main characters. Since it's about him in the past, he is central to the story. His friends like Sasuke and Sakura might also be involved in some way. And of course, characters from the past like the Sannin (Jiraiya, Tsunade, and Orochimaru) could play important roles as they are key figures in Naruto's world history.
Sasuke is also frequently a central character. His complex relationship with Naruto and his own motives can be further delved into within the context of the Mugen Tsukuyomi. For instance, how he might respond to a world created by the illusion that goes against his beliefs or goals.